1. Field of the Invention
The invention relates to a device and method for inserting data and, in particular, to a data insertion method which inserts predetermined pattern data, such as digital watermarking data, to digital image data compressed by MPEG2 (Moving Picture Experts Group 2).
2. Description of the Related Art
Conventionally, a kind of data insertion devices (circuits) are used to insert data to digital image data.
Some of the conventional devices provide digital watermarking by inserting pattern data into MPEG2 data including a sequence of pictures each of which belongs to one of I picture (Intra picture), P picture (Predictive picture), and B picture (Bidirectionally predictive-coded picture).
However, the conventional devices have a problem that a quality of image deteriorates.
The reason is that, a data amount of the pattern data inserted into a P picture is larger than an data amount of the pattern data inserted to an I picture, considering a decoding procedure of each picture, and therefore, in the P picture, there becomes a large difference between the P picture in which the pattern data are inserted and the original image data to be included in the P picture.
Moreover, when the data amount of the pattern data inserted into each picture varies, it seems that a moving picture resulted from a series of pictures waves.